1. Field of the Invention
The present invention generally relates to refrigerant recovery, recycle, and recharge (R/R/R) units and more specifically to an R/R/R unit incorporating an oil-less compressor.
2. Description of Related Art
In 1992, the United States EPA set up regulations requiring the capture (recovery) of all refrigerants from commercial and automotive refrigerant containing systems. Refrigerant Recovery, Recycle, and Recharge equipment (commonly referred to as R/R/R Equipment) has been designed for use on Commercial and Automotive Refrigerant containing systems. Since it is illegal to vent CFC, HCFC, HFC and HFO type refrigerants into the atmosphere, equipment has been developed to recovery, recycle, evacuate, flush, and/or recharge these refrigerants. The equipment can perform one or more of these functions. Some of the more common refrigerants serviced in the mobile Air Conditioning and refrigeration markets are R-12, R-22, R-134a, R-152a, R-404a, R-500, R-502 and R-407C.
Commercially available refrigerant recovery units, which are preferably brought on-site, typically consist of some combination of a recovery compressor, air-cooled condenser, and a fan from which compressed and condensed refrigerant is sent to a collection tank. These refrigerant recovery units are often times configured to recover a wide variety of refrigerants including R-12, R-22, R-134a, R-404a and R-410A among others. In the case of these multi-refrigerant R/R/R machines, single circuit and dual circuit have been utilized. Dual-circuit machines are typically not convertible but rather provide two dedicated refrigerant R/R/R circuits whereby the user selects which refrigerant circuit to utilize. Typically, a dual-circuit system is used to handle two types of refrigerants in order to avoid cross-contamination and is not convertible in any respect; the user selectively engages the circuit that he wishes to employ. Each circuit in a dual-circuit system typically includes each of a compressor, condenser, fan, and tank.
Single-circuit units, on the other hand, employ a conversion process which allows the system to clear out residual refrigerant from a first process before switching over to a different refrigerant in a second process. Many of these single-circuit systems employ oil-filled compressors and filter driers which oil and filter drier desiccant will absorb and hold residual refrigerant absent some cleaning or conversion process. Failure to properly clear out a system will lead to cross contamination of refrigerants and lead to equipment failure. Thus, without an adequate conversion process or the availability of a second circuit, cross-contamination will occur, ultimately leading to equipment damage and failure. On solution, however, is to provide a “recovery-only” unit when dealing with contaminated refrigerant. This allows for the recovery, i.e. capture and storage, process only and will not provide for the recharging or recycling of usable refrigerant back into the system or into another system. Thus, these “recovery-only” systems are limited in use.
There have been several attempts at providing single-circuit multi-refrigerant R/R/R units, however none have adequately addressed the trapped residual refrigerant found in the compressor oil and the filter drier desiccant. For example, the U.S. Pat. No. 5,161,385 to Schumacher describes a refrigerant recovery system that stores and processes the recovered refrigerant in a vapor phase at low pressure and ambient temperatures. The system removes oil, moisture, air and other contaminants from the recovered refrigerant. However, the system relies on the compressor of the refrigerant system being serviced to send the refrigerant out, known as passive refrigerant recovery. Accordingly, if the system being serviced is not operational, the invention cannot work.
U.S. Pat. No. 5,211,024 to Manz et al. describes an apparatus for the purification of a single refrigerant type utilizing a filter/drier unit for removing water from refrigerant passing therethrough. A refrigerant pump, such as a compressor, pumps refrigerant from equipment under service. An oil separator is provided at the outlet of the compressor to remove oil from the processed refrigerant. The refrigerant exits the oil separator and passes through a condenser before it is stored as a liquid in a storage tank. The oil separator must be placed post-compressor in order to remove oil from the refrigerant. However, residual refrigerant will still be retained in the oil sump of the compressor as well as in the oil separator.
U.S. Pat. No. 5,282,366 to Reilly, Jr. et al. describes a hand-transportable unit for transferring refrigerants between containers including a pump, a condenser, and a compressor which operates the pump. The compressor utilized is an air compressor configured to as a pump driving means to operate the pump, which pumps drives the refrigerant from a refrigerant source, through a compressor, and into a storage tank. However, the system provide no means to clear refrigerant from the oil and residual refrigerant will remain in the system after use.
U.S. Pat. No. 5,325,675 to Manz et al. describes a refrigerant recovery system including a compressor having an inlet and an outlet, and an oil separator connected to the compressor inlet for separating oil from refrigerant recovered from equipment under service. A check valve is connected between the outlet port of the separator and the inlet of the compressor for feeding refrigerant directly to the compressor inlet. Pressure sensors are located throughout the system to monitor the refrigerant pressure. A second oil separator may be located post-compressor to remove any additional oil contaminants in the refrigerant after compression. Again, the use of the oil separator in the post-compression stage indicates the existence of residual refrigerant in the oil sump and in the separator after use.
U.S. Pat. No. 5,548,966 to Tinsler describes a refrigerant recovery system having a closed-loop refrigeration system employing a portable storage tank to recover refrigerant from a separate system that needs servicing. A storage tank within an evaporator is cooled by evaporator coils and evacuated by a vacuum pump. The pump is valved off and recovered refrigerant is directed to the storage tank from the separate system. The system assures that none of the recovered refrigerant contacts the compressor of the recovery system and vacuum pump. The system therefore assures that the containments recovered by the recovery system do not come into contact with the recovery compressor, it requires two separate circuits whereby the first is shut off before the second is turned on. These added complexities are undesirable from a cost and maintenance standpoint.
U.S. Pat. No. 6,603,223 to Murray et al. describes refrigerant handling system having a refrigerant compressor with inlet for connection to a refrigerant source to be recovered and an outlet for connection to a refrigerant storage container. A separator is connected in series with the compressor for separating lubricant from refrigerant either before or after passage of the refrigerant through the compressor. A valve is connected between the inlet and the outlet of the compressor for equalizing pressure across the compressor during non-operation. While simple and useful, the need for the oil separate assures that residual refrigerant will remain in the oil sump, separator and other components after use.
Consequently, there is a marked need for single-circuit refrigerant R/R/R unit that does not allow for the build up or recirculation of residual refrigerant after use such that the unit can convertibly handle a plurality of different refrigerants without the need for servicing. It is, therefore, to the effective resolution of the aforementioned problems and shortcomings of the prior art that the present invention is directed. However, in view of the heat exchanger systems in existence at the time of the present invention, it was not obvious to those persons of ordinary skill in the pertinent art as to how the identified needs could be fulfilled in an advantageous manner.